The bogus security software programs often offer a free scan that falsely says a user's computer is infected. If installed, the programs are ineffective against malicious software. Security experts have theorized that those behind the programs reap lucrative profits.
Microsoft detected two Trojan horse programs, Win32/FakeXPA and Win32/FakeSecSen, masquerading as security software on more than 3 million computers in the last six months of 2008, according to the company's Security Intelligence Report, published every six months.
With the Washington state attorney general, Microsoft launched eight lawsuits in September 2008 aimed at tracking down those responsible for perpetrating the scams.
Software vulnerabilities dropped 3 percent in the last half of 2008 compared to the first six months of the year, the report said. But more than half of all of the vulnerabilities were considered "high severity" under the Common Vulnerability Scoring System (CVSS). Also, more than half of those problems were considered pretty easy to exploit, putting Internet users at greater risk.
Microsoft software contained six of the top 10 browser-based vulnerabilities used by hackers against computers running Windows XP.
Hackers also continued to try to exploit older vulnerabilities in Microsoft applications. The most frequently exploited flaw in Microsoft Office, CVE-2006-2492, was patched more than two years ago yet is still targeted by 91.3 percent of attacks against the software suite.
In 2008, Microsoft released a total of 78 security bulletins that fixed 155 vulnerabilities, which represented a 16.8 percent increase over 2007, Microsoft said.
Attackers also looked to exploit problems in other third-party software from vendors such as Adobe, whose PDF (Portable Document Format) reader is widely used. Adobe has had several security vulnerabilities over the last year in its Reader product. Microsoft said it saw more than double the number of attacks aimed at PDF in July 2008 as it did in the whole six months prior.
Vulnerabilities in Microsoft Office file formats and PDFs are golden for hackers, since people can often be persuaded to open the documents using social engineering tricks via e-mail. Microsoft said more than 97 percent of e-mail messages are unwanted because they either contain malicious attachments, are spam or promote a phishing site.
The U.S. remained the No. 1 country for hosting phishing sites, the report said. The state of Texas hosted the most of all, according to Microsoft.